What is prevention?
Every day, we take steps to prevent unwanted events from happening. For example, we brush our teeth to prevent cavities. We would like to ensure some events never happen, but the best we can do is lower our risk. We know people who brush their teeth can still get cavities.
We do what we can to improve the chances of a good outcome, but we don't always have complete control. The same concept applies to cancer and other chronic diseases. In the public health setting, the term “prevention” mainly refers to lowering the risk of getting a disease rather than completely removing the risk. You may also hear the term “risk reduction.”
Risk factors and prevention
Cancer tends to be caused by a combination of factors. Some factors we may be able to control (like exercise), some are out of our control (like age) and some are still unknown.
Since many factors drive cancer risk and we can control only some of these, we cannot avoid some amount of risk. For example, the two most common risk factors for breast cancer, being a woman and getting older, are not things you can control.
For breast cancer, most risk factors that we have some control over have only a small effect on risk. This means there is no one behavior that will prevent breast cancer. But, it also means there's no one factor that will cause it. Even a woman with a BRCA1 or BRCA2 gene mutation doesn't have a 100 percent chance of getting breast cancer. In fact, most people diagnosed with breast cancer are at average risk and we don’t know which factors came together to cause the cancer.
Because the disease process is so complex, it's hard to pin down how a certain set of risk factors will affect a person. When we look at groups of people it becomes clearer. For example, if we find there is a 20 percent decrease in risk of breast cancer in one group of people, we can predict there will be a 20 percent decrease in risk in a similar group. What we don't know is which specific people in the group will get the prevention benefit.
Who benefits from prevention?
It’s hard to know who benefits from prevention. We know some behaviors can lower the risk of cancer, but we don’t know how great the benefit is for any one person. For example, non-smokers are much less likely to develop lung cancer compared to smokers. However, we do not know who prevents lung cancer by not smoking and who would have remained cancer-free even if they had smoked. Further, most smokers will never be diagnosed with lung cancer and some non-smokers will. So, taking steps to prevent cancer lowers risk, but it does not ensure a person never develops the disease.
A healthy lifestyle
The good news is there are some healthy behaviors that are under our control that may reduce the risk of breast cancer. And, making healthy choices can lower the risk of other types of cancer as well as many other chronic diseases such as diabetes and heart disease.
Learn more about healthy behaviors and breast cancer risk.